code: def ssd_300_vgg16_atrous_custom(
      classes,
      pretrained_base=True,
      pretrained=False,
      transfer=None,
      **kwargs,
  ):
      """SSD architecture with VGG16 atrous 300x300 base network for COCO.
  
      Parameters
      ----------
      classes : iterable of str
          Names of custom foreground classes. `len(classes)` is the number of foreground classes.
      pretrained_base : bool or str, optional, default is True
          Load pretrained base network, the extra layers are randomized.
      transfer : str or None
          If not `None`, will try to reuse pre-trained weights from SSD networks trained on other
          datasets.
  
      Returns
      -------
      HybridBlock
          A SSD detection network.
  
      Example
      -------
      >>> net = ssd_300_vgg16_atrous_custom(classes=['a', 'b', 'c'], pretrained_base=True)
      >>> net = ssd_300_vgg16_atrous_custom(classes=['foo', 'bar'], transfer='coco')
  
      """
      if pretrained:
          warnings.warn(
              "Custom models don't provide `pretrained` weights, ignored."
          )
      if transfer is None:
          kwargs["pretrained"] = False
          net = get_ssd(
              "vgg16_atrous",
              300,
              features=vgg16_atrous_300,
              filters=None,
              sizes=[21, 45, 99, 153, 207, 261, 315],
              ratios=[[1, 2, 0.5]]
              + [[1, 2, 0.5, 3, 1.0 / 3]] * 3
              + [[1, 2, 0.5]] * 2,
              steps=[8, 16, 32, 64, 100, 300],
              classes=classes,
              dataset="",
              pretrained_base=pretrained_base,
              **kwargs,
          )
      else:
          from ...model_zoo import get_model
  
          net = get_model(
              "ssd_300_vgg16_atrous_" + str(transfer),
              pretrained=True,
              **kwargs,
          )
          reuse_classes = [x for x in classes if x in net.classes]
          net.reset_class(classes, reuse_weights=reuse_classes)
      return net
  
imports: from __future__ import absolute_import
  import warnings
  from .ssd import get_ssd
  from .anchor import LiteAnchorGenerator
  from .vgg_atrous import vgg16_atrous_300, vgg16_atrous_512
  from ...data import VOCDetection
label_desc: Use image node_id 3 for calling a global function with example usage: ssd_300_vgg16_atrous_custom(classes, pretrained_base, pretrained, transfer) and returns: net